Analysis of scoliosis screening in Dublin (1979-1990) of patients who passed significant levels (25 degrees and 40 degrees) and received orthotic treatment or surgery. To reexamine the basis of school scoliosis screening. The United States Preventive Services Task Force questioned the validity of school screening for adolescent idiopathic scoliosis because there is insufficient scientific evidence to justify it. New entrants (1986-87) to the screening program were used to test the validity of the screening methods. The total screened population, proportions reaching significant Cobb angles or undergoing treatment, were compared across the time period. The sensitivity of the forward bend test in detecting or predicting 40 degrees scoliosis was 0.83, the specificity was 0.99, and the predictive value was 0.08. The proportion prescribed braces declined significantly (P < 0.01), but there was no significant change in those with scoliosis greater than 24 degrees (0.18%) or 39 degrees (.08%) nor was there a significant change in the numbers needing surgery (.045%). The incidence of significant scoliosis and of surgery is low and independent of changes in bracing policy. The validity of screening to cause significant change in prevalence must be challenged.